VW Passat Heater Core Replacement-Clogged Core-Low Heat
A heater core is a radiator-like device used in heating the cabin of a vehicle. Hot coolant from the vehicle's engine is passed through a winding tube of the core. Fins attached to the core tubes serve to increase surface for heat transfer to air that is forced past them, by a fan, thereby heating the passenger compartment.
The heater core is made up of small piping that has numerous bends. Clogging of the piping may occur if the coolant system is not flushing or if the coolant is not changed regularly. If clogging occurs the heater core will not work properly. If coolant flow is restricted, heating capacity will be reduced or even lost altogether if the heater core becomes blocked.You can see from the photos this core was fully 3/4 blocked, doesn't make for good heat on cold Maine mornings.
Because the heater core is located under the dashboard inside of the vehicle and is enclosed in the ventilation system's ducting, servicing it requires disassembling a large part of the dashboard, which is rather time-consuming.